If it is lymph, it is usually species (Genus?) specific, and can spread to other Vieja, but usually not other genera.
Stress will make it spread, anything from too high a temp, too high nitrates, or an alpha fish harassing the one with the virus can make it worse.
As said above, its a virus, so only a virus-cide is an effective in treatment.
You could try rubbing the infected areas with Acyclovir, but the stress of netting and being caught may be more of a negative than the efficacy of the treatment.
I had some Vieja present from the stress of shipping (it is ubiquitous, like the common cold in fish) and it went away quickly with daily water changes, and a stress free tank.